In power semiconductor devices, for example, IGFETs (insulated gate field effect transistors) a load current typically flows in a vertical direction between two load electrodes formed at opposite sides of a semiconductor die that includes a weakly doped drift layer. A dopant concentration in the drift layer results from a tradeoff between blocking capability and on-state resistance of the semiconductor device. Field plate structures extending from a front side into the semiconductor die deplete a portion of the drift layer in the blocking mode such that the dopant concentration in the drift layer can be increased without adverse impact on the blocking capability. Shrinking stripe-shaped field plate structures to needle-shaped field plate structures increases an active transistor area and allows the gate structure to form a grid with larger channel width compared to stripe-shaped gate structures.
It is desirable to further improve the performance of power semiconductor devices.